ext/misc/anycollseq.c

   1 /*
   2 ** 2017-04-16
   3 **
   4 ** The author disclaims copyright to this source code.  In place of
   5 ** a legal notice, here is a blessing:
   6 **
   7 **    May you do good and not evil.
   8 **    May you find forgiveness for yourself and forgive others.
   9 **    May you share freely, never taking more than you give.
  10 **
  11 *************************************************************************
  12 **
  13 ** This file implements a run-time loadable extension to SQLite that
  14 ** registers a sqlite3_collation_needed() callback to register a fake
  15 ** collating function for any unknown collating sequence.  The fake
  16 ** collating function works like BINARY.
  17 **
  18 ** This extension can be used to load schemas that contain one or more
  19 ** unknown collating sequences.
  20 */
  21 #include "sqlite3ext.h"
  22 SQLITE_EXTENSION_INIT1
  23 #include <string.h>
  24
  25 static int anyCollFunc(
  26   void *NotUsed,
  27   int nKey1, const void *pKey1,
  28   int nKey2, const void *pKey2
  29 ){
  30   int rc, n;
  31   n = nKey1<nKey2 ? nKey1 : nKey2;
  32   rc = memcmp(pKey1, pKey2, n);
  33   if( rc==0 ) rc = nKey1 - nKey2;
  34   return rc;
  35 }
  36
  37 static void anyCollNeeded(
  38   void *NotUsed,
  39   sqlite3 *db,
  40   int eTextRep,
  41   const char *zCollName
  42 ){
  43   sqlite3_create_collation(db, zCollName, eTextRep, 0, anyCollFunc);
  44 }
  45
  46 #ifdef _WIN32
  47 __declspec(dllexport)
  48 #endif
  49 int sqlite3_anycollseq_init(
  50   sqlite3 *db,
  51   char **pzErrMsg,
  52   const sqlite3_api_routines *pApi
  53 ){
  54   int rc = SQLITE_OK;
  55   SQLITE_EXTENSION_INIT2(pApi);
  56   rc = sqlite3_collation_needed(db, 0, anyCollNeeded);
  57   return rc;
  58 }